97 E320 really rough idle and backfire at idle.
 

I got my timing cover resealed and drove the car to the car wash and thank god oil leak was fixed. The car had a mix of 10w and 5w-30 from when the oil light flicked 2days earlier on and I shut down the car and coasted into a gas station. Anyway the car was running great except for the rpm going up and down at idle, which I found was a vacuum leak after I shut the car off in my garage. I noticed my cam advance thing wasnt plugged in all the way so I plugged it in. Then when I restarted the car it was really rough and backfired. I tried unplugging the cam advance thing and it was still the same.

Any ideas?

Did you wash the engine? It won't tolerate water getting under the coil cover and into the spark plug holes.

You may also have another issue, possibly with the wiring harness, look for cracked wire insulation at the connectors, and tap on the mass airflow sensor while car is running, if the idle changes or surges drastically you most likely need a new mass airflow sensor.

Your vacuum line may not have the been the cause of the running complaint.